<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<EditText android:text="EditText01" android:layout_height="wrap_content" android:layout_width="fill_parent" android:id="@+id/edtInput"></EditText>
<LinearLayout android:id="@+id/LinearLayout01" android:layout_height="wrap_content" android:layout_width="fill_parent" android:gravity="center">
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Show" android:id="@+id/btnShow"></Button>
<Button android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="Clear" android:id="@+id/btnClear"></Button>
</LinearLayout>
</LinearLayout>

package com.studio.android;
import android.app.Activity;
import android.app.AlertDialog;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class HelloAndroid extends Activity {
  /** Called when the activity is first created. */
 Button btnShow;
 Button btnClear;
 EditText edtInput;
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    
    btnShow=(Button)findViewById(R.id.btnShow);//控件与代码绑定
    btnClear=(Button)findViewById(R.id.btnClear);//控件与代码绑定
    edtInput=(EditText)findViewById(R.id.edtInput);//控件与代码绑定
    btnShow.setOnClickListener(new ClickListener());//使用点击事件
    btnClear.setOnClickListener(new ClickListener());//使用点击事件
  }
  
  class ClickListener implements OnClickListener
  {
   public void onClick(View v)
   {
   if(v==btnShow)
   {
    new AlertDialog.Builder(HelloAndroid.this)
    .setIcon(android.R.drawable.ic_dialog_alert)
    .setTitle("Information")
    .setMessage(edtInput.getText())
    .show(); 
   }
   else if(v==btnClear)
   {
    edtInput.setText("HelloAndroid");
   }
   }
  }
}